New charcoal making furnace (retort?)

New charcoal making furnace (retort?)

Tried out my new charcoal furnace this last weekend, and it seems to work okay.

I've been disappointed with the old technique for making charcoal for a long time. Seems like I went thru tons of fuel and made too much nasty, billowing clouds of smoke for the couple of cubic feet of charcoal I
got. I felt I could do better than that.

I started with a 24" by 40" tank that had already been converted into a wood stove. I punched some more holes in that to accommodate a 48" by 14" propane cylinder. I
cut the bottom off the propane cylinder and fitted it up with a mate collar and a gasket (made from welder's drop cloth). Effectively gasketing that joint is the only tricky part of this assembly. I also replaced the valve with some
¾" black iron piping that I routed back around underneath the smaller tank within the fire box, and drilled some holes in that. The idea was that the gasses evolving off the wood in the smaller tank would contribute to the fuel heating it.

Here is a CAD sketch of the basic structure.

Separating the wood to be converted into charcoal from the heating fire also would mean that I could burn
household trash, yard waste and other wood unsuitable for charcoal and still end up with clean charcoal.

As I said, it worked okay. It still took a handful of hours and it
still smoked rather a lot, though now it was more from the dried resinous scotch broom and rhododendron bush trimmings I was using as fuel. I wasn't sure how well the feedback line was working during the bulk of the run but as you can see in this picture taken late
in the process, it seemed to be working fine.

As an unexpected side benefit I noticed black goo dripping from the seal on the inner tank. I collected about ½ cup of wood tar from that. I haven't decided what to do with it
yet, but I've got it, and I know it should be useful for some stuff. I happened to choose to make this batch of
charcoal from splintered Indonesian hardwood pallet boards. It will be interesting to see if I get different tars from
different feed stocks. Or different performance from the charcoal, for that matter.

Here is one more picture taken at the same time as the last, but showing more of the furnace.

So basically the smoke from the charcoal is being used to heat the charcoal?
Thats very clever, id of never thought of that.
As for the tar ive used tar from a campfire that had settled in a bin lid to cover my old dirty axe handle to stop rotting, i just heated the handle and
painted it on. It looks ok but the handle was real dirty and i wouldnt really do it on a really nice axe.
Jamie

Wood gas is interesting stuff. I've seriously considered building a forge based on the Dasifierdesign, but I really don't need one.
I'd be doing it solely to satisfy my inner geek, who loves to play with all the various ways of making metal hot. And while that's fun, there are only
so many hours in the day and I have to draw the line somewhere. But as long as you're playing with charcoal-making . . .

The gas that evolves off the wood turning to charcoal is made up of turpens, tars, and other gasses not unlike natural gas, all of which burns to give the nice
yellow flames or a regular wood fire. Rather than let it burn with the charcoal (as in a regular fire) nor letting it go up in smoke (as with most techniques
for making charcoal), I recirculated it back into the fire box as additional fuel. I'm not altogether sure I'm getting enough air in there to support
the combustion though. Maybe why the fire is still smoking so much. I've a notion how to fix that.

Matt, that is a cool looking rig for using wood-gas. The potential of the stuff burned separately from the source wood seems to be something most folks forget
about. Think I'll just settle for a crucible nestled into my forge though.

Todd et al,

I ran another batch this last weekend. The first batch didn't quite fully convert, but I opened it too soon. The second batch yielded 100% conversion,
and such nice, clean charcoal I've not seen in my previous efforts.

I haven't forged much lately, in part because I needed the extra incentive to finish the charcoal retort. Now that it is done and I am restocked, it is
time to get back to work.